Weed and grass trimmers have been developed which employ a rotatable hub, with a short length of flexible nylon or other plastic line extending from the hub. When the hub is rotated (typically, at speeds from 6,000 RPM to 12,000 RPM), the tip of the line extending from the hub provides the cutting or trimming action. Weed and grass trimmers using this principle of operation have become popular for their versatility of use, and because the flexible trim line is safer to use than rigid rotating steel blades.
Various types of devices have been developed for using such trimmer lines. Typically, rotating line trimmers or rotating string trimmers employ a line which generally has a circular cross section. In many hand-held trimmers, the line is wound on a storage reel in the hub of the device, and is fed out of a hole in the hub in discrete amounts, as the end wears off or breaks off. Trimmers of this type sometimes are referred to as “bump-and-feed” trimmers, since, when the line breaks off, the bottom of the storage reel is bumped on the ground to cause a spring release of the line within the trimmer. A short length of line then is played out through a hole in the hub by means of centrifugal force when the trimmer is operating. Typically, bump-and-feed string trimmers use relatively small diameter line, normally in the range of 0.065″ to 0.080″ diameter, since the smaller diameter flexible line functions better for the centrifugal feeding of a bump-and-feed head.
Generally, heavier diameter line (for example, 0.115″ to 0.160″) is too stiff for winding and for the centrifugal feeding used in bump-and-feed heads. An advantage of bump-and-feed heads is that less frequent reloading of the line, theoretically, is required than for trimmers using short segments of a predetermined length.
A problem exists, however, with bump-and-feed trimmers in that frequently the line which is wound tends to become stuck, either due to partial fusion of the line within the hub, caused by high frequency vibration, or by successive turns of the line wound on the hub becoming somewhat entangled. As a result, feeding of the line from the hub, when desired, does not always take place. When this occurs, it is necessary to remove the hub from the string trimmer device and manually extract the desired length of line, prior to re-attaching the hub to the device. This is a time consuming and frustrating experience for many users of flexible line string trimmers.
For commercial use, employing relatively large diameter lines, for example 0.115″ to 0.160″ diameter, fixed length line or cut line trimmer heads usually are employed. The large diameter monofilament nylon lines are particularly useful where weed and grass growth is dense. The large diameter lines also provide longer length of service before the line needs to be replaced. A type of heavy duty machine which has been designed for commercial use is a high-wheeled machine, where the motor and operating mechanism is carried between a pair of wheels. The trimmer head extends forward of the wheels, and then downwardly toward the ground, where relatively large diameter fixed or cut lengths of line are inserted into the trimmer head for effecting the trimming operation.
In most cases, either for standard hand-held gas or electric trimmers, or for high-wheeled commercial brush trimmers, when line is to be reloaded, the unit is at rest with the head facing upward. Most trimmers require bottom or side loading. This requires the machine to be tilted upwardly. This is awkward and the machine is heavy to hold. In addition, because of the inverted position of the machine, the possibility of gasoline spillage is ever present.
Bottom loading machines also preclude the utilization of replaceable ground spacers of different heights, since such ground spacers need to be attached to the underside of the head. Another disadvantage, particularly with commercial machines, is that the heavy duty line which is used is difficult to bend and load into the machines. A popular machine employs three closely arrayed semi-circular loops secured to the face of the trimmer head, near its perimeter. To replace line, it must be passed through the three loops in a generally knotted configuration to extend both ends of a fixed cut length of line outwardly from the same side of the head. The sharp bends which are required for insertion of the line make both insertion of a new line and removal of a depleted line difficult, particularly when the larger sizes of line mentioned above are used with such a machine.
The United States patent to Fogle 6,035,618 is directed to a fixed line trimmer head for overcoming the disadvantages present in conventional bump-and-feed heads, and also for permitting use of lines of different diameters in the same trimmer head. The Fogle head, however, requires loading and replacement of the line from the bottom or underside of the head, thus causing it to be subject to the disadvantage of awkward bottom loading, for the reasons discussed above.
It is desirable to provide an improved fixed length line trimmer head for string trimmer machines, which overcomes the disadvantages of the prior art, which may be loaded from the top, which is capable of utilization with lines of different diameters, and which securely holds fixed segments of line in place during use.